Carbon fiber spars including spinnaker poles and masts are known in the art. Carbon fiber spinnaker poles have been used for a number of years and are generally made in two pieces on tapered male mandrels, or in some instances on male mandrels which are then placed in female molds. The pole pieces are generally formed from resin pre-impregnated sheets which may include either woven carbon fiber or unidirectional carbon fibers on a paper backing. The wider ends are connected together, usually with glue or resin pre-impregnated carbon fiber tape to form a pole tapered toward each end. These spinnaker poles do not include sail attaching grooves but are designed to hold a sail or sail leads outboard of the boat. Fixtures mounted at ends of the pole connect the pole to the sail or sail lead.
Carbon fiber masts are also known. One such design is illustrated in prior art FIGS. 5 and 6. As illustrated in FIG. 5, these masts are made with two longitudinally extending pieces or halves which are glued together, after curing, to form the mast circumference. Each of the pieces is laid up by hand from resin pre-impregnated carbon fiber sheets in a female tool. It is necessary to make the prior art mast in two pieces because this permits access to the inside surface of one of the mast pieces for gluing the groove mold and laying-up the sail-attaching groove. The mast piece is cured prior to gluing and lay up.
In other prior art carbon fiber mast designs, the mast is a tapered tube which does not include a sail-attaching groove. Instead, the sail is provided with a sleeve which fits over the tube, or a track is attached to the finished mast for slidingly receiving cars attached along an edge of the sail. These designs are generally overly built and thus disadvantageously excessively heavy. Sleeve type sail attachment prevents the use of rigging to support the mast requiring over building for large masts to be supported. Addition of tracks and cars means excess weight on the mast.
Carbon fiber spars, and especially masts, provide improved performance on sailboats as compared with more typical aluminum masts due to the well known high strength and low weight properties of carbon fiber. Reducing weight in a sailboat mast is important because it reduces the pitching moment by a factor of the square of the distance to the center of mass of the boat. Boats with high pitching moments perform poorly in a seaway. A prior art carbon fiber mast of given size and strength will weigh about one-half as much as an aluminum mast of similar size and strength, providing a sizable reduction in pitching moment and consequent improvement in performance.
Notwithstanding these advantages, most sailboat design classes, measurement rules, and performance or other handicapping systems have banned prior art carbon fiber masts as too expensive due to the time and labor required to lay up the mast by hand, to lay up the mast in pieces, to pre-core a piece of the mast, to glue in a groove mold, to lay up the groove mold or spacer by hand, and/or to glue the pieces together.
Another disadvantage of prior art carbon fiber masts is that the inside surface of the mast may be rough and irregular due to the hand lay-up process. This rough surface may snag or abrade the halyards and other sail control lines which pass within the mast, accelerating wear, and necessitating more frequent replacement.
The manual construction of prior art masts may provide a varying thickness around the circumference and along the length of the mast which may cause irregular flex characteristics. Similarly, manual construction may lead to nonreproduceable flex characteristics among a series of masts intended to be identical. Manual manufacturing may also introduce defects into the mast such as air pockets which may lead to premature breakage. The glue used to combine mast pieces or components may fail in the harsh sailing environment of temperature extremes and salt water, causing spar failure and possibly injuring sailors. Further, manual manufacture may increase material costs in requiring glue, excess carbon fiber, excess resin, and may also increase material costs due to wastage and spoilage of resin pre-impregnated carbon fiber sheets which may have a limited shelf life.
What is desired, therefore, is a carbon fiber spar having an integral sail-attaching groove which may be economically formed in order to attain the performance advantages of carbon fiber at little or no additional cost as compared with aluminum. Such a spar would likely be approved for use in virtually all design classes, measurement rules and handicapping systems. Providing the spar with a smooth inner surface and forming the spar without a gluing step, multiple coring steps, and manual carbon fiber lay up are also desirable.